This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Huntington's disease (HD) is a disorder characterized by motor and psychiatric dysfunction. Clinical phenotypes at advanced stages include increased development of choreic movements and dementia. This study is directed at determining biomarkers in neurodegenerative disease. Previous studies showed increased levels of oxidative damage markers in HD. There is evidence that intermediates in the serotonin pathway produce free radicals and contribute to oxidative damage and that other intermediates in this pathway play a neuroprotective role. Initial studies suggested the possibility that oxidized 5-hydroxytryptophan (5-HTP) products bind to protein in HD. Oxidized 5-HTP products were found to form adducts with angiotensin. The suggested reaction site of the oxidized 5-HTP is at the meta-position on tyrosine. Equine apomyoglobin, was reacted with 5-HTP in an EC synthesis cell. The eluent was subsequently collected and digested with trypsin. The parallel LC/EC-LC/MS system was used to elucidate structures of conjugated apomyoglobin Oxidized 5-HTP products were found to form adducts on a fragment with m/z 1884.061. We have found that an offline EC synthesis cell can be used effectively to produce oxidation products of 5-HTP and reaction products with proteins. Adducts are being characterized by to-down sequencing on the LTQ-Orbitrap and by peptide mapping. In a second study, the metabolites of sodium phenyl butyrate, a drug currently in clinical trials for treatment of HD, and endogeneous metabolites elevated by SPB treatment, were determined in plasma and urine samples of patients over the course of treatment. This system serves as a model for investigating redox reactions and metabolic pathways that occur as a consequence of disease state. A detailed paper that describes the identification of unknown metabolites and other components that vary between controls and patient samples, was published in Analytical Biochemistry (EN Ebbel et al., Anal Biochem. 2010, 399, 152-161.).